One of the methods for improving the productivity in a method for producing a target substance by a fermentation process includes a method for modifying the ability of uptake of a sugar which is a starting material.
A research on the mechanisms of uptake of a carbohydrate such as a sugar by a microorganism has been advanced, and the mechanisms are known to be classified into several types. These include, in particular, a phosphoenolpyruvate:sugar phosphotransferase system (hereinafter also referred to as PTS or phosphotransferase system), which is a transporter which phosphorylate and thereby take up a major sugar (Non-Patent Document 1).
The PTS system is composed of a substrate-independent common system EI (encoded by ptsI), HPr (encoded by ptsH), and a substrate-specific component EII (Non-Patent Documents 2 to 4).
The substrate-specific component EII varies in type depending on organisms, however, with respect to enteric bacteria and coryneform bacteria, with which a research has been advanced, major EII enzymes are being identified, and among these, a fructose-specific EII is known to be encoded by FruA (PtsF) (Non-Patent Document 5).
It is known that the fructose uptake by the PTS system requires FruA which externally take up fructose and converts it into fructose 1-phosphate as well as FruK (PfkB) which converts fructose 1-phosphate into fructose 1,6-bisphosphate serving as an important intermediate in glycolysis (Non-Patent Documents 6 and 7).
With respect to the production of a substance, several reports in which the productivity is improved by modifying the PTS system have been known. For example, a process for producing an amino acid using a bacterium of the genus Escherichia with enhanced ptsG gene (Patent Document 1), and a process for producing an amino acid using a bacterium of the genus Escherichia with enhanced crr gene which functions in the same manner as ptsH, ptsI, and, ptsG (Patent Document 2) are known.
Further, a method for accelerating uptake and metabolism of a sugar which does not go through the PTS system, such as pentose or the like, by disrupting the PTS system which is the uptake system of the major sugar, glucose or the like, is known (Patent Document 3).
Further, it is known that the productivity of a target substance can be increased by disrupting the PTS system, which is the glucose uptake system, to lead to uptake via another pathway and thereby changing the metabolic pathway of the sugar (Patent Document 4). It is also known that the productivity can be increased by disrupting the fructose uptake system and introducing a foreign fructokinase and thereby changing the metabolic pathway of the sugar (Non-Patent Document 5).
However, it has not been known that a target substance can be efficiently produced by disrupting the PTS uptake system of a specific sugar to improve the ability of uptake of another sugar by the PTS system. Further, it has not been known that the ability of uptake of another sugar is increased when the PTS uptake system and a metabolic pathway after uptake are disrupted simultaneously. In particular, since glucose plays a central role in controlling sugar uptake, even if the uptake system is simply enhanced, there arises a problem that the uptake rate decreases as the intracellular glucose concentration increases, and therefore, it has been predicted that it is difficult to improve a glucose consumption rate (Non-Patent Document 8).